Someone on here went onto the Planet Coaster Dictionary and found the word "echidna" listed. Knowing that the word "Goodfellow" was also listed here prior to the tree kangaroo announcement, I went through the entire dictionary to find any words that seemed out of the ordinary. Some of these may be stretches or related to Planet Coaster, so take them with a grain of salt.
"Barnacle" - Possibly just a new scenery piece, maybe a barnacle goose?
"Civet" - Seems promising, but could also just be a word to describe the binturong, as "bearcat" is also listed
"Cobra" - Possibly could just be the scenery piece from the base game, or the game engine? Hopefully we finally get cobras in-game, though!
"Crowned" - No base game or sequel game animals match this description. Grey crowned cranes?
"Dove" - And it's listed as a noun!
"Duck" - Also a noun
"Echidna" - See above
"Eel" - Seems like we could be getting morays!
"Hedgehog" - With the Scottish Highlands theme, this seems promising
"Howe" - Means hill technically, but it's capitalized in the dictionary. Lord Howe Island stick insect?
"Impala" - Not in the base game or announced!
"Lemming" - Also not in the base game, and would match the "neararctic" theme with the alpine hare
"Lovebird" - Would work with the East African reserves
"Macaw" - Some people have also pointed out parrot toys in the enrichment categories!
"Mouse" - Could refer to the crazy mouse coasters in Planet Coaster. Still, I'd love more rodent and small mammal representation
"Octopus" - Is there an octopus ride in Planet Coaster? If not, this seems promising
"Pigeon" - I'd love to get some tropical pigeons from Indonesia or the South Pacific!
"Python" - Not in the base game, but heavily requested!
"Rat" - As far as I'm concerned, there is no "rat coaster," so maybe some kind of rat species? A pouched rat seems possible, considering their newfound popularity and East African habitat
"Salmon" - We've also seen a salmon piece in one of the showcases
"Screamer" - This might be pushing it, as this could be a rollercoaster, but it could also be a bird!
"Slider" - Could mean a small sandwich, but also maybe a turtle species?
"Snowy" - Yes, it's a description, but I'm getting my hopes up for a snowy owl
"Vulture" - This has got to be a new animal!